Natural Resources
Conservation Service
Ecological site F145XY002MA
Silty Low Floodplain
Accessed: 05/07/2024
General information
Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
MLRA notes
Major Land Resource Area (MLRA): 145X–Connecticut Valley
The nearly level floor of the Connecticut River Valley makes up most of the area. Nearly level to sloping lowlands are at the outer edges of the river valley. These lowlands are broken by isolated, north- to south-trending trap-rock ridges that are hilly and steep. Elevation ranges from sea level to 330 feet in the lowlands and from 650 to 1,000 feet on ridges.
Recent alluvium has been deposited on the nearly level flood plain along the Connecticut River since the glacial retreat about 10,000 to 12,000 years ago. These deposits created some of the most productive agricultural soils in New England. Glacial lake deposits, outwash, and recent alluvial deposits dominate.
The area primarily supports central hardwoods. Habitat loss and fragmentation are widespread throughout the lower part of the Connecticut River Valley. The major tree species in the rest of the forested areas are sugar maple, birch,beech, oaks, and hickory. White pine and hemlock are the dominant conifers, but pitch pine and red pine are more common on sandy soils. Red maple grows on the wetter sites.
The most common understory plants are moosewood and hobblebush in the northern part of the area and dogwood in the southern part. Abandoned agricultural land is dominated by white pine and paper birch in the northern part and red cedar and gray birch in the southern part. The important upland habitats include trap-rock ridges and sand plains. Oak woodlands and cedar glades are common on the ridges. Black oak savannas mixed with pitch pine and varying amounts of little bluestem are common on the sand plains. Other habitats of significance include wetlands associated with the Connecticut River freshwater marshes, swamps, flood plains, and lowlands. The dominant trees on the flood plains are black willow, cottonwood, and sycamore.
Large mammals, such as white-tailed deer, moose, and black bear, are in the forests in the northern part of this area. Animals that are tolerant of human settlement are numerous throughout the rest of the MLRA. Examples are white-tailed deer, opossum, skunk, raccoon, and coyote.
Classification relationships
USDA NRCS:
LRR: Northeastern Forage and Forest Region
MLRA 145 Connecticut Valley
USDA USFS:
Province221: Eastern Broadleaf Forest
Section 221A: Lower New England
Subsection 221Af: Lower Connecticut River Valley
EPA Ecoregions:
Level III: 59 Northeast Coastal Zone
Level IV: 59a Connecticut Valley
Ecological site concept
The site consists of deep, coarse-silty, moderately well drained, alluvial soils on low floodplains of mostly large river valleys but can occasionally be found within small river valleys. These floodplains are subject frequent to occasional flooding and for longer duration than high floodplains. Representative soil is Winooski.
The reference community is a deciduous forest dominated by silver maple with cottonwood occurring sporadically within the tree layers. American elm and green ash are found as low trees. Northern spicebush, southern arrowood and silky dogwood are can be found in the shrub layer. Sensitive fern can dominate the forest floor. Additional species include sweet reedgrass, white avens, white turtlehead, jewelweed and various sedges (Metzler and Barrett 2006). Pin oak, green ash, and American sycamore will be more common within small to medium river valleys. River types such as large, low gradient and small-medium low and high gradient rivers differ in hydrologic regime and fluvial geomorphology and consequently have different community composition (Marks et al. 2011).
The frequency, duration, and timing of floods is the primary natural disturbance affecting species composition. Floodplain forests are commonly found in early to mid-successional stages because of the dynamic nature of floodplains (Thompson and Sorenson 2000). Young alluvial forests are typically dominated by eastern cottonwood along major rivers or American sycamore in small to medium sized rivers.
Invasive exotic plants are a significant threat to the community since many can successfully displace native species. Common invasive exotic plants are Japanese barberry, Norway maple, Oriental bittersweet, European bush honeysuckle, garlic mustard, and Japanese stiltgrass.
Table 1. Dominant plant species
Tree |
(1) Acer saccharinum |
---|---|
Shrub |
Not specified |
Herbaceous |
(1) Onoclea sensibilis |
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